Explanation:
Why do comets emit X-rays?
First discovered
during the passing of
Comet Hyakutake in 1996,
the reason a cold
comet
would produce hot
X-rays has since remained a mystery.
On July 14, however, the orbiting
Chandra X-ray Observatory was able to
provide an image of passing
Comet LINEAR,
shown above, in enough detail to unravel the mystery.
The key to the
solution turns out to be the unusual
wind of fast ions emitted by our
Sun.
These
ions apparently collide with gas recently emitted by the
comet and cause some ions to
acquire a new
electron.
An
electron
that starts in a high-energy state will emit an
X-ray as it falls in closer to the ion
nucleus.
As other comets move into the inner Solar System, this discovery should allow
future study of the continually evolving gas cloud that surrounds
comets as well as the composition of the
solar wind.